Game Freezing - Starcraft, Zerg Campaign

I don't know if this belongs here, but ever since I had virus problems and especially RUNDLL problems, I can't play my game. My computer is fit to run WoW at a decent level, but now I'm just playing the original Starcraft. I got through the terran campaign just fine, but when I play the Zerg campaign, once I beat the first level, my game freezes. I ran memtest, upgraded my drivers and uninstalled/reinstalled the game, and I still have problems with the first Zerg level. I beat it about 7 times, but never completed it. Any ideas? It is something with the Zerg?